Convective cushion with positive coefficient of resistance heating mode

ABSTRACT

A cushion that is heated convectively using a positive coefficient of resistance type resistive heating element that is provided with heat exchanging surfaces, includes a mattress pad, seat or the like with a bottom surface secured around its perimeter to an air permeable top surface, forming a plenum and containing tubular spacer material therein. The plenum is connected to a power unit housing a blower, a heating module and a controller unit. The heating module preferably includes a PTC type heating element in conduction with a base plate and a number of heat exchanger fins. Preferably the heating element is sandwiched between a pair of the base plates and the heat exchanger fins, and there is a seal between the base plates to minimize air flow from the blower from passing there between. A remote control for the user&#39;s convenience may be provided, and a foldable antenna attachable to the convective unit facilitates wireless communication between the remote control and controller unit. The user resting atop the cushion is able to control the blower and heating module to deliver air of a desired temperature and quantity to the cushion and through the top surface. The invention advantageously replaces the current carrying, conductive wires and insulation found inside prior art heated mattresses, enhancing safety and performance while at the same time offering a cooled or ventilated capability.

CROSS REFERENCE TO RELATED DOCUMENTS

This application is continuation-in-part of utility patent applicationSer. No. 11/024,073 (filed Dec. 27, 2004) entitled “Variable TemperatureCushion And Heat Pump.”

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to temperature controlled mattress pads,seats or other cushions, and more particularly to such a cushion that isheated by a positive temperature coefficient (PTC) element andventilated as well.

2. Description of the Related Art

Resistance wires oftentimes with PTC resistive elements are theconventional way of heating a cushion by conduction. This suffers fromcertain disadvantages, however, including that the electrical conductorsare located within the cushion itself. Over time, the wires, carbonfiber strips or the like being subject to repeated weight loads andmechanical stresses may become physically damaged causing sparks fromshort circuits, and an occasional fire. Voltages as low as 6V canproduce noticeable sparking, even at current levels in the 1-200milliamp range.

Insulation is commonly used in the prior art, not only to limit peakheating at the conductor but also to spread the heating effect out (oraverage it) over the surface to be heated. The disadvantage here is thatit takes longer to reach an adequate heating level, because of the dropin heating efficiency caused by the insulation. The overall efficiencyof the heating apparatus is compromised as the insulation slows theheating of the outer surface of the cushion.

Additionally, resistance heated type, prior art mattress pads don'toffer cooling or ventilation. This is a major disadvantage in many partsof the world where the population lacks means such that air-conditioningis unavailable and a substantial portion of the year relaxing orsleeping is uncomfortable due to very warm ambient air conditions.

OBJECTS OF THE INVENTION

Accordingly, it is an object of the present invention to construct atemperature-controlled cushion that is heated without the conventionalresistance wires or PTC resistive elements in conductive mode within thecushion itself,

It is a further object of the present invention to construct such acushion while minimizing the use of insulation.

It is a still further object of the present invention to provide such acushion that also includes a cooled or ventilated mode.

It is a still further object of the present invention to provide such acushion that includes convenient controls for the user.

It is a still further object of the present invention to provide such acushion that is simple and relatively inexpensive to manufacture.

It is a still further object of the present invention to provide anaccompanying power unit that is quiet and compact, and located remotefrom the cushion;

These and other objects of the present invention will become apparentupon reference to the following detailed description and accompanyingdrawings.

SUMMARY OF THE INVENTION

Disclosed is a new approach for a cushion that is heated convectivelyusing a positive coefficient of resistance type resistive heatingelement that is provided with heat exchanging surfaces, or alternativelya thermoelectric device with heat exchanging surfaces, or a StirlingCycle heat pump with PTC heater mounted on the cold head and heatexchanging surfaces attached to the PTC heater and/or cold head.

The present invention includes a mattress pad, seat or other cushionwith a bottom surface secured around its perimeter to an air permeabletop surface (forming a plenum or air-flow structure) and containingtubular spacer material or equivalent therein. The plenum has an openingfor a (preferably insulated) air duct which leads to a power unithousing a blower, a heating module and a controller unit. Besidesobvious uses in the home or an automobile, the invention as disclosedherein may also be used for patient warming in medical and surgicalsettings.

The heating module preferably includes a PTC type heating element inconduction with a base plate and a number of heat exchanger fins.Preferably the heating element is sandwiched between a pair of the baseplates and the heat exchanger fins, and there is a seal between the baseplates to minimize air flow from the blower from passing there between.A remote control for the user's convenience may be provided and afoldable antenna attachable to the convective unit facilitates wirelesscommunication between the remote control and controller unit, althoughcorded remote control may also be utilized or the controls located onthe power unit itself. The power unit may include multiple PTC elementsincluding of varying capability to allow the user to more preciselycontrol the output temperature of the air, and may include a speedcontrol for the blower.

The user resting atop the cushion is able to control the blower andheating module to deliver air of a desired temperature and quantity tothe cushion and through the top surface. The advantages of the subjectinvention over the prior art in heating mode for mattress pads, seatsand other cushions are substantial. Since there are no currentconducting wires or carbon fiber strips within the cushion structure,the convective cushion is much safer than the prior art when used as amattress pad. This is because the PTC heating element is locatedremotely from the cushion and is connected to the cushion only with anair duct hose, eliminating all mechanical stress to any electrical wiresfrom weight applied to the sleeping or seating surface. Because theheating medium is air, and not hot current conductor wires, it isn'tnecessary to use insulation to spread the heating effect over the entiresurface of the cushion. By using air, the heating effect is gentle andeffective without the need for insulation, so the overall heating modeefficiency is higher and more evenly distributed over the heatedsurface.

The present invention, besides replacing basic electric resistance wireheated mattress pads as well as other resistance element heatedcushions, also offers a feature that the prior art cannot using the sameequipment and that is a ventilation mode for warm weather. By causingambient air to move within the air flow structure (which is much moreefficiently done with tubular spacer fabric as described elsewhereherein, and in U.S. Pat. Nos. 6,263,530 and 6,085,369, but can be doneless efficiently with other air flow structure materials), a meaningfulpercentage of excess body heat can be removed during warm weather whilethe user is seated on or sleeping on the cushion of the subjectinvention.

As long as ambient temperature is below the user's body skin temperature(which averages out to approximately 96 degrees Fahrenheit over much ofthe body), there must (according to Newton's Law of thermal transfer),be a thermal exchange between the source of heat at a higher temperature(body skin surface), and a heat sink at a lower temperature, by ambientair under forced convection (macrocosmically) and free convection,(microcosmically). The terms macrocosm and microcosm simply refer to therelatively large bulk air flow (or forced convection), produced throughthe cushion air flow structure by the blower and the relatively verysmall air convection movement (free convection), produced at themicrocosmic level by the delta T or difference in the relatively warmair nearest the user's skin and the relatively cool air brought intoclose proximity via forced convection. The microcosmic level is thatlevel within the padding and textiles which is the interface between theuser and the air flowing through the cushion.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a side elevation view of the convective cushion of thepreferred embodiment of the present invention placed atop a conventionalmattress;

FIG. 2 is a plan view of the convective unit with a portion of thehousing removed to show its contents;

FIG. 3 is an enlarged plan view of the PTC resistive heating element 30;

FIG. 4 is an end view of the assembly of FIG. 3;

FIG. 5 is another side elevation view of the same assembly, in the airflow direction, looking through the heat exchanger fins;

FIG. 6 is a cross-sectional view of the air duct;

FIG. 7 is a side view of the convective unit with an optional attachablefolding antenna with an attached air duct hose 40 to convey conditionedair to the cushion.

FIG. 8 is a side view of a convective seat cushion for a vehicle with acompact power unit installed at the bite line between the seat andbackrest in accordance with an alternate embodiment;

FIG. 9 is a side view of the power unit optionally installed at thefront of the seat;

FIG. 10 is a cross-sectional view of the power unit optionally installedat the top of the backrest;

FIG. 11 is a front elevation view of the cushion with a damper valve forregulating the airflow;

FIG. 12 shows the modified airflow of FIG. 8 when the damper valve isclosed;

FIG. 13 shows the modified airflow of FIG. 9 when the damper valve isclosed; and, FIG. 14 shows the modified airflow of FIG. 10 when thedamper valve is closed.

LISTING OF REFERENCE NUMERALS

-   convective cushion 10-   plenum 12-   air impervious bottom surface 14-   air-permeable top surface 16-   vent 17-   tubular spacer material 18-   power unit 20-   housing 21-   blower 22-   circuit board box 24-   adaptor 26-   air outlet 27-   air duct inlet 28-   PTC resistive heating element 30-   heat exchanging fins 32-   power terminals 34-   PTC heating element 36-   base plates 38-   air seal or gasket 39-   air duct hose 40-   flexible air duct 42-   insulated sleeve 44-   sleeve splines 46-   remote IR sensor, detector 50-   length of wire 52-   articulated folding strut, antenna 60-   IR sensor 62-   adapter plug 64-   hinge points 66-   vehicle seating cushion 130-   seat rest 132-   backrest 134-   compact power unit 150-   straight air duct 194-   special air duct 195-   special duct 196-   Zipper™ valve or damper 198

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Initially referring to FIG. 1, shown is the convective cushion 10 placedupon a conventional mattress, including a plenum 12 constructed of abottom surface 14 secured around its perimeter to a top surface 16. Thebottom surface 14 is preferably air impervious, although placement on aconventional mattress may render an air permeable surface largelyimpervious. The top surface 16 is air-permeable although sufficientlyimpervious that a greater air pressure can be maintained inside theenclosed space.

Inside the plenum 12 is tubular spacer material 18 or equivalent. U.S.Pat. Nos. 6,085,369 and 6,263,530 pioneered the use of such tubularspacer fabric 18 as an air flow structure for seats, mattresses,mattress pads, and other articles of furniture that can be sat on orlaid down upon. Although the preferred embodiment of this inventionutilizes the same tubular spacer fabric 18 as described in the issuedFeher '369 and '530 patents, it is possible to utilize other air flowstructures such as Muller Textile's 3 Mesh or Strahle and Hess'assembled woven tube fabric, as well as any other air flow structure;however there may be substantially reduced levels of performance whencompared to tubular spacer material 18 as disclosed in the above U.S.Pat. Nos. and herein.

FIG. 2 shows a power unit 20 for the convective cushion 10, whichincludes a blower 22 for blowing air across one a PTC resistive heatingmodule 30 including heat exchanging surfaces 32 (see FIGS. 3-5), andpushing the air into the plenum 12 for heating the cushion 10.Alternatively, the PTC module 30 need not be energized, resulting in aventilating function as a result of circulating ambient air through thecushion air flow structure 12. The PTC heating module 30 with heatexchanging fins 32 is located in an adaptor 26 that matches the module30 to the blower air outlet 27 and the air duct inlet 28 in the mostaerodynamically efficient manner within the space limitations of thepower unit 20 housing 21 dimensions. Details such as a power cord andplugs and sockets are not shown.

Also shown in FIG. 2 is a box 24 for any necessary or desired electricalcircuits for mode switching, switching between multiple heaters, on andoff, etc., plus wireless remote control circuits if desired. A speedcontrol printed circuit board may be incorporated in the space 24 shownin FIG. 2, which could be used to control heating as well as ventilationby coordinating PTC elements with AC power control to regulate air flow,perhaps offering more flexibility in comfort settings than the simplestform which relies solely on the PTC switch temperature characteristicsof the PTC elements with a fixed air flow rate.

The box 24 may optionally include a Triac or other semiconductor powercontrol for the PTC heating elements to enable the PTC elements tooperate below their switch temperature design point. The PTC elementswitch temperature is the temperature at which the resistance starts torise exponentially. The elements 36 are called Positive TemperatureCoefficient because, unlike NTC, or Negative Temperature Coefficienttype materials, the electrical resistivity rises with increasingtemperature, instead of dropping with increasing temperature. Mostmaterials exhibit PTC characteristics because increasing temperaturecauses more ionic movement, crystal lattice vibration, and/or molecularmotion, any of which can interfere with electron mobility. The switchtemperature of ceramic PTC devices is determined by the amount of dopingwith certain elements, such as strontium, for example, before firing.

In order to operate the PTC heating elements 36 below their design pointswitch temperature it is necessary to either increase the heat loadbeyond the capabilities or rating of the elements, by increasing airflow beyond the design point for example, or by reducing voltage to theelements, which reduces the power rating of the elements relative to theload. For a mattress pad application of the convective cushion 10 it maybe more desirable to use a power reduction instead of an air flowincrease, in order to maintain a very low noise level for a comfortablesleeping environment.

FIG. 3 shows the PTC heating module 30 with heat exchanging fins 32running in the Y axis and power terminals 34 on the right side. Two PTCelements 36 can be seen, represented by dashed lines, mounted in themiddle of the heat exchangers 32. The preferred PTC elements 36 arerated 50 Watts each and 120 VAC, with a switching temperature of about38-45 deg. C. max., and are manufactured by Advanced Thermal Products,Inc. of Saint Mary's, Pa. Other elements with different power andvoltage ratings can be used; however the above is the preferredembodiment because it is unnecessary to produce air at more than about45 deg. C. max. to affect good heating performance and using elementsrated for 120 VAC eliminates the need for a power supply which reducesthe cost of the product while increasing product reliability. If a morepowerful heating effect is desired, it is a simple matter of usinghigher rated elements or more of the same power rated elements 36.

FIGS. 4, 5 show the PTC heating elements 36 mounted between two baseplates 38 of the heat exchangers 32. These plates 38 are heavier thanthe fins 32 and serve to spread the heat outward from the PTC heatingelements 36 to the far edges of the heat exchangers 32 as efficiently aspossible without excessive thickness and weight. An air seal or gasket39 is also shown in this view the purpose of which is important. Theseal 39 prevents air flow between the two heat exchangers 32, whichforces all of the air flow through the fins 32, increasing thermaltransfer efficiency. The reason that this became an issue was that thethickness of the PTC heating elements rated for 120 VAC is twice that ofPTC heating elements rated for 12-24 VDC. The extra thickness results ina gap of sufficient size to permit excessive air flow between the twoheat exchanger base plates 38. The seal 39 addresses this issue toproduce a more efficient apparatus that operates reliably at or veryclose to the switch temperature.

The PTC heating module assembly 30 can be made with a single heatexchanger 32; however such an arrangement would not be as efficient froma thermal point of view. The heat exchangers 32 are preferably made ofcopper, although aluminum or any other thermally and electricallyconductive material can also be used. Although solder can be used tobond the PTC heating elements 36 to the heat exchanger base plates 18, aflexible adhesive with good thermal and electrical conductivity ispreferred to prevent excessive stress buildup and possible PTC element36 cracking due to differences in coefficient of thermal expansion (CTE)between the PTC heating element 36 material and the heat exchanger 32material, which can be substantial, for example, approximately 10:1 forthe PTC elements 36 and copper.

Referring back to FIG. 1, the power unit 20 may be mounted on the floor,with a flexible air duct hose 40 attached to one end of the convectivecushion 10, which is preferably at the foot of the bed. Although it ispossible in some instances to introduce air into the convective cushion10 at the head of the bed it is preferred to put the air in at the footof the bed for several reasons. The power unit 20 is designed to be veryquiet, however it is not totally silent so the father away it is fromthe user's ears the better. For heating mode, the extremities tend torequire more heating than the trunk of the body; therefore putting thewarmed air in at the foot puts the warmest air in at the place whereit's needed most, the extremities, or feet and legs. Lastly, there maynot be enough space between the bed and the wall at the head of the bedto accommodate the air duct hose 40.

FIG. 1 shows how some of the air percolates or vents up through thecushion 10, which is enclosed in a textile envelope 12 and secured to,in this case, a bed, resulting in ventilating or heating air flowingunder the covers (not shown), however most of the ventilating or heatingair flows through the cushion 10 air flow structure 18 and vents out atthe end 17 opposite from where it entered.

FIG. 1 also shows how to achieve an infra-red type remote control withthe convective cushion 10 as a mattress pad. Ordinarily, the power unit20 is placed on the floor at the foot of the bed in order to enable ashort length of air duct hose and to minimize blower noise perceived bythe user. Unfortunately, this places the power unit 20 out of the lineof sight of an infra-red (IR), type remote control, which is lessexpensive than a radio frequency (RF), type remote. The more expensiveRF remote has the advantage of not requiring a line of sight tofunction. Shown is connecting a remote IR sensor, or detector 50, to thepower unit 20 with a length of wire 52 (most beds are at least 6 feet inlength, so the length of wire 52 needed is at least that long, plusapproximately three feet for slack), to enable the user to use an IRremote (not shown) without a line of sight to the power unit 20.Alternatively, either an IR or RF type remote may be designed to be usedwith the PTC power unit 20 in order to enable control of ventilation, orheating, and degrees of ventilation and heating, without the need for acord connecting the remote to the power unit 20.

The solution of FIG. 7 is to place an IR sensor 62 on the end of anarticulated folding strut, or antenna 60, attached to the power unit 20.When the antenna 60 is unfolded vertically, the user has a line of sightto the IR detector or sensor 62, enabling use of the IR type remotecontrol. The IR sensor strut 60 should be capable of extendingvertically at least 24 inches or more, and can be attached to the powerunit 20 permanently or can use an adapter 64 to plug into the power unit20 housing before or after unfolding. A telescopic strut (not shown)could also be used, but managing the wire on the inside during collapseof the telescopic type of antenna is more complex and bulky than using afolding strut 60 with rotary electrical contacts at the hinge points 66.The folding antenna 60 design can be such that the middle leg folds tonest within the top leg and the bottom leg folds to nest within themiddle leg, etc. The legs can be made of flat strips of metal or plasticwith the top leg overlapping the middle one and so on. Power to thesensor 62 and signals from the sensor 62 can be transmitted to thecontrol circuit 24 in the power unit 20 via either wires in the antenna60 or via the arms of the antenna 60 and a third wire if the arms aremade of conductive material or if they are provided with conductivecircuit traces and rotating contacts in the joints.

FIGS. 1, 6 and 7 show the PTC heater assembly 30 with blower 22connected to the mattress pad 10 via a length of flexible air duct 40. Agood example of such an air duct 42 is known as Uniloop, made byFlexhaust, Inc. It is important for good performance of the preferredembodiment 10 to ensure that there is low heat loss in the air duct 42in cold weather and in heating mode. Although there are numerousmaterials and techniques that can be used to make a flexible insulatedair duct for the purposes of the subject invention, one example is tomake an insulation sleeve 44 for the Uniloop air duct hose out ofVolara, made by Voltek Corp., which is a polymeric foam with very smallclosed cells enabling a relatively high R rating, or insulation ratingfor a relatively thin material cross section. In this case a Volarasleeve or layer approximately 0.08″ thick produces very good results. Apreferred form of the Volara insulation sleeve 44 would be extruded withinternal splines 46 as shown in FIG. 6 to create small air gaps betweenthe sleeve 44 and the air duct 42 to enhance the insulation performanceof the sleeve with minimal bulk.

This is one way of making an insulated air duct hose 40 for thepreferred embodiment 10 that remains flexible and non-bulky whileenabling higher performance and efficiency for the subject cushion ormattress pad in heating mode under cold ambient air temperatureconditions. However it is configured, an insulated air duct hose 40 isimportant for best cold weather heating mode performance, especiallybecause the air delta T in heating mode is substantially higher than inventilation mode, in which there is no delta T because ambient air isbeing used for ventilation. If a source of air cooled below ambient isused, then the insulated air duct 40 will improve efficiency, however,not to the same extent, as active cooling mode delta T will stillusually be less than half that of heating mode delta T. For example,heating mode may easily entail an air delta T of 45+ deg. F., whileactive cooling mode with thermoelectric or Stirling Cycle devised asdisclosed in some of my other patents, will generally not exceed 20-30deg. F.

Referring to FIGS. 8-14, an alternate embodiment vehicle seating cushionmay be described, in particular application of the PTC air heating andventilating system to a seat cushion consisting of a seat rest andbackrest capable of sustaining internal air flow that will communicatethermally and convectively with the user contacting surfaces, incommunication with the PTC power unit or air heating and ventilatingsystem, via a variety of optional air pathways. As shown in FIG. 8,preferably a compact power unit 150 is installed proximate the “biteline” or separation between the seat rest 132 and backrest 134 portionof the cushion 130, with a straight air duct 194 running from the mouth162 of the power unit 150 to the cushion 130. This set up is preferredas conditioned air entering the middle portion of the cushion 130 ismore easily evenly distributed throughout the seat rest 132 and backrest134. Alternatively, the power unit 150 can be installed forward of theseat rest 132 with a special air duct 195 (FIG. 9) or above and aft thebackrest 134 with special duct 196 (FIG. 10). These configurations areuseful for use with seats that do not have an opening or slot at the“biteline” between the seat and backrest cushion of the seat upon whichthe PTC cushion is to be installed, in order to facilitate installationof the cushion.

Note the airflow direction through the cushion 130 varies depending uponwhere the power unit 150 is placed, with the air primarily exiting thecushion 130 remote from the power unit 150. The set up with the powerunit 150 forward the seat rest 132 is advantageous for ease of controlin that the power unit 150 controls could be located directly on theunit 150 and easily accessible between the user's legs when seated onthe cushion 130. When the power unit 150 is located aft of the user, awired control extends to the user or to a location accessible to theuser or a remote wireless control could be used.

FIG. 11 shows a Zipper™ valve or damper 198 installed in the middleportion of the cushion 130. The damper valve 198 serves to control theair flow between the seat rest 132 and backrest 134 portions of thecushion 130. For example, when the power unit 150 is installed at thebite line and the valve 198 is completely closed, air flows only throughthe backrest 134 and not the seat rest 132 (FIG. 12). Other examples,when the power unit 150 is installed atop the backrest 134 and the valve198 closed air flows again only through the backrest 134 (FIG. 13), orwhen the power unit 150 is installed forward the seat rest 132 and thevalve 198 closed air flows only through the seat rest 132 (FIG. 14), inboth these instances the air exiting the cushion 130 through the duct194 at the bite line. It is also possible to open or close the valve 198to intermediate positions in order to vary the thermal effect of thecushions, by controlling the amount of air flowing through the cushions.

The present invention has been described in connection with preferredand alternate embodiments, but it is understood that modifications willoccur to those skilled in the appertaining arts that are within thespirit of the invention disclosed and within the scope of the claims.

1. A selectively-controlled convective cushion comprising: a plenumdefined by a bottom surface secured around its perimeter to a generallyair permeable top surface and containing tubular spacer materialtherein; a power unit located remote from the plenum but in fluidcommunication with the plenum, and housing a blower in fluidcommunication with a heating module; a controller unit in communicationwith the blower and the heating element; whereby a user resting atop thecushion is able to control the blower and heating module to deliver airof a desired temperature and quantity to the cushion and through the topsurface.
 2. The selectively-controlled convective cushion of claim 1wherein the plenum has an opening at one end, and further comprising anair duct with one end sized to be received into the plenum opening and asecond end extending to the power unit.
 3. The selectively-controlledconvective cushion of claim 1 wherein the heating module comprises a PTCtype heating element in conduction with a base plate and a plurality ofheat exchanging fins.
 4. The selectively-controlled convective cushionof claim 3 wherein the heating element is sandwiched between a pair ofthe base plates and the plurality of heat exchanging fins.
 5. Theselectively-controlled convective cushion of claim 4 further comprisinga seal between the base plates to minimize air flow from passing therebetween.
 6. The selectively-controlled convective cushion of claim 1further comprising a remote control in communication with the controllerunit.
 7. The selectively-controlled convective cushion of claim 6further comprising a foldable antenna attachable to the power unit tofacilitate wireless communication between the remote control andcontroller unit.
 8. The selectively-controlled convective cushion ofclaim 8 wherein the controller unit includes a speed control for theblower.
 9. The selectively-controlled convective cushion of claim 2wherein the air duct comprises an outer shell and an inner insulatingsleeve with an air gap there between.
 10. The selectively-controlledconvective cushion of claim 1 further comprising a vent at the opposingend of the plenum.
 11. The selectively-controlled convective cushion ofclaim 1 wherein the bottom surface of the plenum is generally airimpermeable.
 12. The selectively-controlled convective cushion of claim1 wherein the plenum is adapted to be placed on a conventional mattress.13. The selectively-controlled convective cushion of claim 3 wherein thepower unit comprises a plurality of PTC type heating elements.
 14. Aconvective mattress pad comprising: a plenum defined by a bottom surfacesecured around its perimeter to a generally air permeable top surface,the plenum containing an air flow structure and having an opening at oneend; an air duct with one end sized to be received into the opening anda second end extending outside the plenum; a power unit housing a blowerin fluid communication with a heating module and connected to the secondend of the air duct; a controller unit in communication with the blowerand the heating element; and, wherein the heating module comprises a PTCtype heating element in conduction with a base plate and a plurality ofheat exchanging fins.
 15. The mattress pad of claim 14 wherein theheating element is sandwiched between a pair of the base plates and theplurality of heat exchanging fins.
 16. The mattress pad of claim 14further comprising a seal between the base plates to minimize air flowfrom the blower from passing there between; and
 17. The mattress pad ofclaim 14 further comprising a remote control in communication with thecontroller unit.
 18. The mattress pad of claim 17 further comprising afoldable antenna attachable to the power unit to facilitate wirelesscommunication between the remote control and controller unit.
 19. Themattress pad of claim 14 wherein the controller unit includes a speedcontrol for the blower.
 20. The mattress pad of claim 14 wherein the airduct comprises an outer shell and an inner insulating sleeve with an airgap there between.
 21. The mattress pad of claim 14 further comprising avent at the opposing end of the plenum.
 22. The mattress pad of claim 14wherein the air flow structure is tubular spacer material.